Cyclic triamines such as aminoethylpiperazine (“AEP”) have many industrial uses. For instance, these compounds are useful as dispersants, epoxy curing agents, chelants, catalysts, accelerators, hardeners, extenders in polymer fabrication, starting materials in the preparation of other amines, starting materials for making pesticides, and the like. AEP is also known by other names including 2-piperazin-1-ylethaneamine; 2-(1-piperazinyl)ethylamine; N-AEP, N-(2-aminoethyl) piperazine; 2-piperazinoethylamine; 1-(2-aminoethyl)piperazine, 1-piperazine ethaneamine, and 1-aminoethylpiperazine.
A variety of processes for making cyclic triamines are known. According to one approach, AEP is a by-product formed from the reaction of ethylenedichloride (EDC) and ammonia or amines to form higher amines. See, e.g., Russian Patent Documents 2226188 and 2186761 and also Khimicheskaya Promyshlennost (Moscow, Russian Federation) (1987), (5) 267-9. However, in these reactions, the amount of AEP produced generally is small relative to the entire product mix. Also, undue amounts of salts can also result. Excessive salt production can complicate purification and/or disposal.
Cyclic triamines can also be formed by reacting hydroxyl functional reactants (e.g., monoethanolamine or ethylene glycol) and/or amines with other amines or ammonia in the presence of acid catalysts at high temperatures, e.g., 300° C. or higher. Acid catalysts include, for example, phosphorous doped, niobium doped, or tungsten doped metal oxides and several mixed metal oxides including zeolites. For example, U.S. Pat. No. 5,256,786 uses a magnesium silicate catalyst with piperazine (PIP) and ethylenediamine (EDA) as feed to produce AEP at 53% selectivity at 9% conversion. U.S. Pat. No. 5,073,635 shows examples of monoethanolamine (MEA) and PIP (1/1 mole ratio) with other metal silicates (Y, La, Ce, Nb, Zr, Ti) with conversions of ˜20-40% and AEP selectivities of 70-84%.
U.S. Pat. No. 4,983,735 claims heteropolytungstates for the MEA+PIP reaction. Fixed bed results show up to 68% conversion of PIP with about 65% selectivity to aminoethylpiperazine (AEP).
U.S. Pat. No. 5,030,740 teaches the use of tungsten oxide/titania for conversion of crude piperazine and MEA to AEP. Here selectivity to AEP is lower in part due to the high MEA/PIP ratio of 1:3, the relatively high conversion of MEA, and the reaction of EDA and diethylenetriamine (DETA) with MEA.
U.S. Pat. No. 4,927,931 has examples based on niobium oxide and niobium phosphate catalysts. Selectivity is lower than with the silicates.
Journal of Catalysis, 144(2), 556-68; 1993 discloses using a H+-pentasil zeolite (Si/Al=25-19,000) at 350 C, a LHSV approximately 0.8 h-1, atm. pressure in a plug flow reactor. Ethylenediamine and its linear and cyclic oligomers result in piperazine and 1,4-diabicyclo(2.2.2)octane (TEDA), with small levels of AEP being formed.
U.S. Pat. No. 5,225,599 discloses a process for the preparation of triethylenetetramine and N-(2-aminoethyl)ethanolamine. This process comprises the condensation of an alkyleneamine and an alkylene glycol in the presence of a condensation catalyst selected from Group IVB oxides or Group VIB compounds and a catalyst promoter. A mixture of silicotungstic acid (18 g), H2O, and TiO2/WO3 (55 g) was heated to 350 to give a catalyst. A mixture of ethylenediamine and ethylene glycol (2.95 mol ratio) was fed into a tube containing the above catalyst at 269.8 and 614.7 psig to give a product containing 6.13% by weight piperazine, 18.71% by weight triethylenetetramine, 47.84% by weight N-(2-aminethyl)ethanolamine; and 2.39% by weight N-(2-aminoethyl)piperazine, and 24.93% by weight other products.
U.S. Pat. No. 4,906,782 discloses a process whereby alkyleneamines having an increased number of alkylene units are prepared by reacting NH3 and/or an alkyleneamine with an alkanolamine in the presence of a Nb-containing catalyst insoluble or slightly soluble in the aqueous reaction solution. Ethylenediamine 90, monoethanolamine 45, and NbO5 1.4 g were heated at 300 for 5 to give piperazine 2.3, diethylenetriamine 59.8, N-(2-aminoethyl)ethanolamine 2.6, —N-(2-aminoethyl)piperazine 1.0, triethylenetetramine (isomers) 15.0, tetraethylenepentamine (isomers) 2.0, and pentaethylenehexamine (isomers) 1.0%, vs: 0.1, 76.0, 23.8, 0, 0, 0, 0, respectively, when using silica-alumina in place of NbO5.
In U.S. Pat. No. 4,922,024 amines (esp. acyclic polyalkylenepolyamines) are prepared by amination of alcohols with reactant amines in the presence of H2 and binary or ternary compounds of Group VIB metals as catalysts. Thus, 50 mL of a mixture of diethylenetriamine (I) and H2NCH2CH2OH (II) (mole ratio 2:1) was autoclaved over 6.3 g WB-WB2 catalyst at 315 and 365 psig H2 for 5.0 h to show 36% conversion of II and the following selectivities (1- and II-free basis): H2NCH2CH2NH2 19, triethylenetetramine 27, tetraethylenepentamine 36, piperazine 7, N-(2-aminoethyl)piperazine 9, and N-(2-aminoethyl)ethanolamine 1%.
U.S. Pat. No. 4,806,517 shows that linear polyethylenepolyamines are prepared by the condensation of ethylenediamine (I) with ethanolamine (II) over a catalyst which is prepared by impregnating Group IVB element oxide pellets with an aqueous solution of a P—O compd. at 20-150° C. so as to bond 0.5-6% of the P to the surface of the pellets in the form of hydroxy-containing phosphate groups, and then calcining at 200-900. A 100 mL solution of 85% H3PO4 was heated to 130° C. under an inert atmosphere, 105 cm3 of TiO2 pellets were added, the mixture reacted for 2 h, and calcined at 600° C. for 16 h. The catalyst was contacted with a 2:1 molar ratio I-II mixt. of 325, producing approximately 65% II conversion with the formation (selectivity %) of piperazine 1.8, diethylenetriamine 59.0, N-(2-aminoethyl)ethanolamine 0.7, N-(2-aminoethyl)piperazine and N-(hydroxyethylpiperazine 2.1, triethylenetetramine 19.6, and tetraethylenepentamine 4.2%.
U.S. Pat. No. 4,584,405 Polyethylenepolyamines are prepared with high selectivity to linear products, from ethylenediamine (I) and ethanolamine (II) using activated C catalysts (optionally pretreated with strong mineral acids).
U.S. Pat. No. 4,552,961 Predominantly linearly extended polyalkylene polyamines are produced by treating alkylenediamines with alkylene glycols or alkanolamines using a P amide catalyst.
Other strategies use reductive amination methods in which alkanolamines are reacted with ammonia and/or alkyleneamines to produce cyclic triamines. Generally, only a small amount, e.g., less than 10 percent, of AEP is contained in the final product mixture. Examples of this practice using hydrogenation catalysts are described in U.S. Pat. Nos. 5,455,352; 5,248,827; and 4,602,091.
It remains desirable to develop strategies for making cyclic triamines with improved conversion and selectivity. It would also be desirable if the reaction conditions could be moderate in terms of temperature, and have improved catalyst stability.